The present invention relates to a device for detecting the change of viscosity of a fluid having the properties of an electrolyte.
More particularly, it is designed to measure the coagulation rate of a blood sample placed in contact with an appropriate reagent.
Numerous solutions have been proposed for measuring the rate of coagulation of blood such, for example, as the introduction of a ferromagnetic ball into the bottom of a cup containing the fluid to be tested, and which is driven with a periodic movement under the effect of an external magnetic field and in which the modifications of the movements of this ball, due to the modification of the physical state of said fluid, are detected.
These devices require the use of centrifuged blood or plasma introduced in an appreciable amount in a cup. Furthermore, the reagents used are lyophilized and must be reconstituted by means of distilled water at the time of their use.
The purpose of the present invention is to overcome this drawback by providing a device of simplified use permitting, on the one hand, ambulatory use for the personal use of patients under supervision who must carry out frequent tests, without using complicated, cumbersome equipment requiring sterilization after use and, on the other hand, making possible integrated tests which may contribute to the total automation in the conducting of analyses: (without reconstitution of the reagent, without conservation problems, etc. . . . )
For this, the invention is based on the depolarizing effect of the electrodes in an electrochemical cell which results from agitation of the electrolyte.
This effect has been ascertained by the Applicant, who has discovered that the voltage at the terminals of such a cell, when it is operating, begins by following a law of evolution characteristic of the polarization phenomenon and then levels out, which means that agitation of the electrolyte has had a depolarizing effect.
The Applicant then discovered that by using, as electrolyte, blood or plasma placed in the presence of a reagent which causes coagulation thereof after a certain time, the levelling out was itself followed by resumption of the normal law of evolution of the polarization curve.
Tests have shown that passing from the level portion to resumption of the normal law was critical and coincided with the instant of coagulation, such as it was determined by a traditional method.
The phenomenon will be the same whenever a liquid electrolyte undergoes a critical variation of its viscosity which will cause it to cease its agitation.
Furthermore, one of the difficulties of chronometric measurements is in being able to detect the zero instant when the plasma or the blood is placed in contact with the reagent. This device gives it straight off since, as soon as the electrolyte is introduced, the battery then formed delivers current which indicates very precisely the time t =0.